Bertens, a qualifier ranked 149th, upended fifth-seeded Simona Halep 6-3, 6-4 behind three breaks. She made a break in the fourth game of the first set hold up and served out after posting a break in the ninth game of the second.
Pous-Tio, No. 110 in the rankings, got past Mathilde Johansson 6-1, 2-6, 7-5 with her seventh break of the day ending the match. She won as many points as Johansson (38-38) off Johansson's serve.
Saturday's winner will be a first-time WTA champion. Pous-Tio holds a 2-1 edge in previous meetings.
The champion of the Grand Prix de Sa Le Princesse Lalla Meryem tournament will earn $37,000 with the runner-up taking home $19,000. Halep and Johansson each claimed $10,200 as semifinalists.